I wouldn't move it until spring if I were you. ETA: Water extremely well before you attempt to move it.

In my experience, these plants are very tough, so don't worry too much about killing it. The roots don't go very deep, and every section is actually an individual plant that has its own root system. Use a turning fork or pitchfork to loosen it from the soil, then keep rocking and loosening until you can safely pull it out. It may fall apart, because like I said, that clump is actually a bunch of individual pieces. If you happen to pull the roots off of one piece, never fear. As long as the base of the shoot is intact, all you have to do is take off a couple of bottom leaves, dip it in rooting hormone, then stick it in the ground or into a pot and keep it watered. It will put out roots pretty quickly, although it may lose a few bottom leaves along the way. New leaves grow from the center of each piece, so as long as that's alive, it will be fine.

Yes, and I doubt you have to really start 4 ft. out, although I'm also not sure exactly where that is. But I'd sink my (sharpened) spade in the ground such that I was actually right at where the clump ends-with the back of the spade towards the plant, trenching around without prying on the ball. Then once you've got a nice trough around it, start to undercut. BTW, this is the manner in which B&B trees and shrubs used to be dug, before tree spades and mechanized digging. Then you will end up with a discreet clump, easy to divide up.